1. Field of the Invention
The present invention relates to a novel polyester multi-filament yarn and a unique fabric made of the same. Particularly, it relates to an improvement of a polyester multi-filament yarn having uneven thickness and to a fabric made thereof having appearance and touch just like a spun silk fabric.
2. Description of the Related Arts
According to recent market needs, a fabric made of a polyester yarn having an improved touch resembling that of natural fibers, such as a silky touch, wooly touch, a cotton-like touch or a linen-like touch has been developed. However, a satisfactory product, especially, one having a raw silk touch has not been obtained.
An oldest woven fabric of polyester filaments is one formed by plain filaments. FIG. 2 is a microscope photograph showing in an enlarged manner the arrangement of filaments on the surface of this known fabric made of plain polyester yarns. As shown in FIG. 2, this fabric has an artificial touch of so-called synthetic fiber-like and has no bulkiness, and the fabric is slippery. Accordingly, the fabric is used for sport wears in which only the toughness is important or in the field of umbrellas or sheets.
As the product in which the defects of the above fabric are eliminated, there can be mentioned a silky fabric formed by a yarn having filaments which differ in shrinkability. Namely, this fabric is characterized in that filaments having a high shrinkability and filaments having a low shrinkability are mixed together and the woven fabric is made bulky by utilizing the difference of the shrinkability at the finishing step of the woven fabric, whereby softness and drape resembling those of silk are imparted to the fabric.
FIG. 3 is a microscope photograph showing in an enlarged manner the arrangement of filaments on the surface of the silky woven fabric formed by the above mixed yarn. As shown in FIG. 3, the single filaments on the surface are slightly bulky, but the individual single filaments are substantially in parallel to one another, and the fabric is still close to the fabric made of a plain filament yarn.
As the product in which manifestation of a wooly touch is intended, there can be mentioned a textured fabric. In this fabric, by imparting fine crimps to respective filaments, wool-like bulkiness and voluminousness are manifested. Since an artificial touch is still left in this fabric, there has been proposed a technique according to which two filament yarns differing in the elongation are simultaneously subjected to the texturizing treatment to form a false-twisted two-layer yarn and a woven fabric is formed by using such yarns. In this fabric, since respective filaments have crimps and they are meandering (migrating), the artificial rubbery touch inherent to the filament woven fabric is eliminated and the touch is made closer to the touch of wool.
FIG. 4 is a microscope photograph showing in an enlarged manner the arrangement of single filaments on the surface of the woven fabric formed by using the above-mentioned false-twisted two-layer yarns.
A woven fabric made of a Taslan (a registered trade mark of Du pont) yarn formed by compressed air texturizing has been developed. This woven fabric is characterized in that loops (closed loops) are formed in single filaments to impart a crispy feel and a cotton-like touch. Moreover, there has been developed a technique of imparting a rigidity by fusion-bonding single filaments to produce a linen-like touch.
FIG. 5 is a microscope photograph showing in an enlarged manner the arrangement of single filaments on the surface of a woven fabric of Taslan yarns. As shown in FIG. 5, loops formed in the single filaments are present on the surface of the woven fabric.
As is apparent from the foregoing description, touches resembling those of most of natural fibers such as silk, wool, cotton and linen can be manifested in polyesters, and therefore, polyester fibers are vigorously used in the field of outwears where these touches are required and polyester fibers are in full flourish at the present.
However, a raw silk touch has not been manifested in polyester fibers at all. A raw silk fabric is rather coarse and crispy but it has an elegant feel. Consumers' needs have been recently diversified and even this peculiar touch is now required. Under this background, we have conducted research with a view to develop a novel technique of manifesting this touch.
While, it is known that an uneven yarn can be obtained when an undrawn polyester yarn is incompletely drawn (see Japanese Examined Patent Publication No. 51-7207 and Japanese Unexamined Patent Publication No. 58-70711). In this uneven yarn, as the unevenness is stressed, characteristics such as touch or unique appearance are strongly manifested. However, if this unevenness is stressed, a lowly oriented undrawn portion is left and the handling property or physical performance is degraded. Accordingly, in a product in which the touch and appearance are strongly manifested, the physical performance is poor.
Of course, the idea of improving the physical performance of the uneven yarn is disclosed in Japanese Examined Patent Publication No. 51-7207, but the attained improvement is still insufficient. More specifically, although an uneven yarn having an elongation of 35 to 70%, in which the total denier is not uneven, is disclosed, the primary yield strength is 1.0 g/d and the shrinkage in boiling water is higher than 15% in this yarn. Thus, this yarn fails to satisfy recent needs of improvement of the quality in connection with the handling property and physical performance.
The present inventors found that the raw silk touch fabric can be obtained by further improving a polyester uneven yarn of the abovesaid type.